THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.

[17:00:00] WOLF BLITZER, CNN HOST: Happening now: new tension in Baltimore. Confusion in the streets as a suspect is arrested and a gun goes off. Police rush to explain what happened, but just a day after a curfew is lifted, can they keep a lid on the situation?

Impossible case -- six police officers have been charged in the death of Freddie Gray. But many people now asking if the prosecutor can get convictions. Will the experts -- why the experts say this is going to be a very tough case.

Texas terror attack -- two heavily armed gunmen, one of whom pledged loyalty to ISIS, storm an event focused on the Muslim Prophet Muhammad. Both assailants are shot dead.

Are others out there?

And North Korean threat -- in a CNN exclusive, we'll take you to the very dangerous frontier between North and South Korea, as the nuclear- armed North warns that in any future war, America will become ground zero.

I'm Wolf Blitzer.

You're in THE SITUATION ROOM.

ANNOUNCER: This is CNN breaking news.

BLITZER: We're following two breaking stories right now. In Texas, we're learning more about the suspect in -- suspects, I should say, in a terror attack near Dallas. At least one linked himself to ISIS. Both were wearing body armor and carrying automatic weapons. They got inside their target and wounded a security guard before an off-duty traffic officer shot and killed them.

Tonight, there are many unanswered questions.

We're also watching an extremely tense situation on the streets of Baltimore. Crowds gathered after police say a man dropped a handgun while he was being arrested and it went off. Our correspondents are standing by. Our experts are working their sources to bring us the late breaking information. And we're standing by to speak with the attorney for the family of Freddie Gray.

But let's begin with CNN's Brian Todd.

He's in Baltimore and has the very latest. -- Brian.

BRIAN TODD, CNN CORRESPONDENT: Wolf, this incident really ramped up the tensions because of everything that has happened here at the corner of Pennsylvania and North Avenues over the past week. The looting and the violence of last week, the protests that had occurred, because of all of that, this incident that occurred a couple of hours ago just ramped everything up more than it really normally would have.

Here's what we know happened. This occurred a couple of hours ago. This information coming from Lieutenant Colonel Melvin Russell of the Baltimore Police.

There was an incident near this intersection of Pennsylvania and North Avenues. Police observed an adult black male walking armed with a handgun. They saw him on closed-circuit TV doing that. They moved to apprehend him. A short pursuit on foot ensued. At some point, the man's gun fell and discharged. It's not clear if it fell as police were upon him or as they were approaching him.

But at some point, the man's gun fell and discharged. There were no injuries. The man was not injured according to police. And they -- he was fused medical treatment. He did not want medical treatment. The police made him go with the ambulance just out of an abundance of caution.

Again, this man has no injuries. The gun went off. One round was spent.

But apparently, according to police, it did not hit them.

The police, according to the officer that we spoke to, Melvin Russell, never discharged their weapons. And, again, this man is unhurt.

Again, this incident, if it had occurred maybe four or five blocks away, maybe at another time of day, another, you know, again, another location, this would not have made much news. But because this happened here at this intersection, it just served to ramp up the tensions a lot more.

There was a police cordon across this street a short time after the incident, Wolf. But right now, no visible police presence at this intersection and things have calmed down considerably.

BLITZER: So basically, police -- people on the streets, Brian, believe what the police say?

They're accepting what the police version of what happened is?

TODD: You're hearing different versions of that, Wolf. Some are accepting it and some are questioning it. But no one is getting overly upset about it. They're going about their business. Traffic is moving normally and, you know, we're going to wait and see if anything occurs.

But right now, the situation is calm and the police have moved out of the intersection.

BLITZER: All right, Brian, thank you.

This afternoon's incident interrupted what Baltimore police hoped would be a return to normal after weeks of trouble and demonstrations. After a busy but peaceful weekend, Baltimore's curfew has now been lifted. National Guard troops are preparing to pull out and stores are reopening.

Our justice reporter, Evan Perez, has been talking with his police sources.

He's joining us for more on what's going on in Baltimore -- Evan, what are you learning?

EVAN PEREZ, CNN CORRESPONDENT: Wolf, you know, they -- one of the things that they know they have is a problem with the community and the trust that they -- that is lacking, frankly. And this incident just underscores that. And, you know, there's a lot of work they need to do, they know.

They're working on trying to provide some information to the public about steps they're going to take to try to reform the police department.

[17:05:05]

We expect that that's going to be announced in the next couple of days.

But as Brian said, you know, this incident quickly, quickly built. There was a crowd that built up at the scene simply because people don't trust the police and people don't trust anything that they say, it appears. And initially, the police themselves were very confused because they were pursuing the suspect. They saw him on the crime camera, what they call crime cameras. And that's why they tried to arrest him. They saw he had a handgun, a revolver. And apparently, according to them, the account that we heard from them, he apparently tried to toss the handgun. And that's when the gun went off.

And, you know, they didn't fire any shots, but it was something that quickly they had to bring in riot police just to make sure that the crowd did not go out of control -- Wolf.

BLITZER: Evan, how are police positioning themselves with no curfew for 10:00 p.m. tonight?

PEREZ: Well, you know, they've pulled back in a lot of the locations. We still see them downtown near the tourist attractions that are the lifeblood of the economy here, Wolf. But there's a lot less police presence here at city hall. You're free to walk into city hall without having to show your identification. So that's a big change from the last week. But other than right there at Penn North, which is that neighborhood where this incident happened today, you see a lot less police presence -- a lot less visible police presence on the streets, Wolf.

BLITZER: All right, Evan.

Thank you.

We'll stay in close touch.

Joining us now in THE SITUATION ROOM is "Billy" Murphy. He's an attorney for the family of Freddie Gray, the man who was fatally injured while in custody of Baltimore police.

Billy, thanks very much for joining us.

We saw an immediate response after a suspect's gun went off on the streets today. You've been listening to all of those reports. Certainly crime has spiked since tensions erupted in Baltimore after Freddie Gray's death. There have been at least eight homicides since last Tuesday, this according to "The Baltimore Sun."

How worried are you that the city right now is sort of still in a tinderbox waiting for something to happen?

WILLIAM "BILLY" MURPHY, ATTORNEY FOR FAMILY OF FREDDIE GRAY: I'm not worried at all, Wolf. This is a great city. And everybody is anxious to get things back to normal. The business community is anxious to get back to normal. The people of the neighborhoods are anxious to get back to normal. Working people are anxious to get it back to normal. And that's the spirit of this city right now, as I gauge it.

And it is particularly impressive that the police appear to have shown tremendous restraint in this latest incident. And that should be communicated, if the facts of it can be verified, as quickly as possible, because people need to know that there's been change. And this may be the harbinger.

BLITZER: As you know, immediately after this incident, there were a bunch of people out in the streets who didn't -- who claimed that the police shot this young man. They didn't want to believe what the police were having to say. I guess the bottom line question is, how much distrust is there in Baltimore between young people, especially out in the streets, and police?

MURPHY: There's a tremendous amount of distrust. There's a tremendous amount of distrust among the adults in Baltimore about what the police will or will not do. And so as quickly as you can verify that this was an incident that was settled without injury and peacefully, the more helpful that reporting will be.

And I don't think any of us need to speculate about it until it can be verified. That would not be a service to the community.

BLITZER: Do you accept the version that the police have now publicly put out?

MURPHY: No, I'm saying just the contrary. I'm saying let's verify it. If the police are correct, let's get it out there as quickly as possible so that people can understand that there's a new day and that the police are showing restraint even under these kinds of circumstances. That would be great news for Baltimore.

BLITZER: It certainly would be.

All right, what -- how is the work...

MURPHY: But it has to be verified, Wolf.

BLITZER: I know you're in close touch, obviously. You represent Freddie Gray's family.

How are they doing?

MURPHY: They are not doing well. They have had moments of real uplifting, for example, when the community rallied behind them and continues to rally behind them. But they're grieving. They're in shock. I mean you can only imagine what it's like to lose a child or to be a sibling and lose a brother.

BLITZER: So what -- are they -- are they, though, reassured, from their perspective, that justice might be served?

MURPHY: We hope justice will be served promptly. And there are two kinds of justice, justice for them and justice concerning the larger issue of these police officers. So we hope that this thing can be resolved quickly so that they can go about their life and they can grieve, hopefully, privately.

[17:10:00]

BLITZER: All right, Billy, if you can, I'd like you to stand by.

We have more questions. I want to review with you what's going on in Baltimore right now.

We'll take a quick break.

Much more with "Billy" Murphy right after this.

(COMMERCIAL BREAK)

BLITZER: Breaking now -- new tensions in Baltimore after police approached a man carrying a gun. Officers say the man's gun fell, discharged. No one was hurt.

Crowds gathered, though, during the confusion. Police came out in force, but things are calm right now.

We're talking with an attorney for the family of Freddie Gray, there you see him.

[17:15:13] We'll speak with Billy Murphy in a moment. Before we resume our conversation with him, though, I want to go to Brian Todd for more now on the second-guessing that's under way, that those six police officers who face charges of what happened to Freddie Gray, that it could be a very, very difficult case.

What are you hearing over there, Brian?

BRIAN TODD, CNN CORRESPONDENT: Certainly could be difficult, Wolf. You know, these streets, as you've seen this afternoon, still pulsating with tension, with a lot of energy. That announcement by the prosecutor's office on Friday. It certainly was a dramatic moment. It touched off street live celebrations, rallies, protests.

But now the hard work of trying to get convictions begins for the prosecution. And legal analysts are telling us that convictions in these cases are by no means a sure thing.

(BEGIN VIDEOTAPE)

TODD (voice-over): The young state prosecutor sounded supremely confident as she dropped the bombshell. Freddie Gray's death, Marilyn Mosby declared, was a homicide.

TODD: But now the work of trying to get convictions begins, and Mosby's cases against the six officers are by no means slam dunks.

ANDREW ALPERSTEIN, FORMER BALTIMORE COUNTY PROSECUTOR: These charges are very tricky to get convictions on especially with this sets of facts.

TODD: Andrew Alperstein's one of two former Baltimore prosecutors we spoke to. He says the second depraved heart murder charge against Officer Caesar Goodson, who drove the van Gray suffered his spinal cord injuries in, will be especially difficult to prove.

ALPERSTEIN: Typically it's described in law schools across country as somebody who would throw a flower pot out a 20th story window on a crowded downtown street. You know, a reasonable person should know that that's going to cause a potential risk to injure somebody or kill them.

TODD: But he says proving Goodson knew beforehand he was creating a specific risk of death for Freddie Gray will be tough. Analysts say many brutality cases against police are difficult to win. In 1992, four L.A. police officers were acquitted on assault in the Rodney King case, even though they'd been videotaped beating him.

Four New York City officers were acquitted of second-degree murder in the 1999 death of Amadou Diallo. They shot him more than 42 times, mistakenly thinking he had a gun. Legal experts say jurors are often sympathetic to police officers

because of the dangerous nature of their work. But the Baltimore officers' lawyers note their city is different.

ALPERSTEIN: I'm sure that's coming. They'll try to get a change of venue in the case, because the juries tend to be, you know, anti- police to some extent in Baltimore.

TODD: Analysts say inconsistencies in witness statements, lack of video in the police van are big hurdles for prosecutors in the Gray case. What's their strong suit against the officers?

JEREMY ELDRIDGE, FORMER ASSISTANT STATE'S ATTORNEY, BALTIMORE CITY: The officers' states attorney will emphasize innumerable requests Mr. Gray made seeking medical treatment. It seems as though that they are really banking on the idea that Mr. Gray petitioned for help and was denied.

TODD: Much will depend on the woman bringing this case. Marilyn Mosby's been the chief prosecutor in Baltimore for only four months. Jeremy Eldridge, who worked for her, says she only had a few years' experience as a trial prosecutor.

ELDRIDGE: She did have some felony experience, but didn't handle any homicides, any wiretapping cases, or any attempted murders. So the question then becomes, can a state's attorney who did not have that experience handle a case of this magnitude?

(END VIDEOTAPE)

UNIDENTIFIED FEMALE: Are you trying to tell me what to do?

TODD: Could Mosby's office get one of these officers or more than one to flip and testify against the others? The local attorneys we spoke to say that could be possible, and if it did happen, it would increase the chances of conviction, but they say so far it's not likely. They say the police have been supportive of one another. They have a long- standing code of honor. And one of the local attorneys we spoke to, a former prosecutor who's got his finger on the pulse of the situation, says so far the attorneys for the six officers have been working together. Of course, that could change -- Wolf.

BLITZER: All right, Brian, thank you. Back with us is Billy Murphy. He's the attorney for the family of Freddie Gray. How difficult of a prosecution, Billy, you're an experienced lawyer in Baltimore. How difficult will this be for the state's attorney?

MURPHY: Well, it depends on the rest of the evidence that she has. Nobody in her position would disclose all of the pieces to the puzzle. She was only disclosed what she thinks she needs to show probable cause. So we can't speculate based on what she has disclosed, how strong or how weak her case is going to be. There is a lot of time between now and the presentation of the evidence to a jury, and many things can happen.

As one of the defense lawyers pointed out, somebody could roll on the rest of the police officers. And this code that they talk about of honor is not a code of honor at all. It is a requirement to be popular and accepted in the police departments of America that you not tell on a police officer if you are a fellow officer, even if the police officer violated the law. That is not a code of honor.

[17:20:11] And so if somebody comes to their senses and they say, for example, "I saw what happened, or I heard what happened." This is what happened. And if it incriminates a fellow officer, I would not be at all surprised if that so-called code of honor, which is really a code of dishonor, crumbles.

BLITZER: What do you make of, we just heard from Brian. She's only been on the job, what, for four months. It's never really prosecuted a homicide. She's only 35 years old, relatively inexperienced. How much of a problem potentially is that?

MURPHY: You know, the assumption in that question is that she is going to personally try this case. Maybe she will. Maybe she won't.

And another assumption is that she would try it by herself without the more experienced prosecutors in her office. Maybe she will. Maybe she won't.

But let's look at what's most likely to happen. She has an extraordinarily experienced team of prosecutors who have been also assisting in the investigation of this case. It is those people that the defense should be worried about, not Marilyn Mosby. And when I say that, I mean that you put your best people on the job, and this isn't a question of her ego politically or otherwise. That's what I think she's going to do.

And so this question is really misplaced, because the assumptions are incorrect, that the outcome or skill and experience that will come out in a courtroom is based on her and her alone.

BLITZER: Will the Gray family, and you represent them, also simultaneously or later file a civil lawsuit against the officers, against the city, for Freddie Gray's death?

MURPHY: That's a question that we haven't answered yet. We're after justice. And so we want to see as much of the evidence as possible before we do anything like that, Wolf. This isn't about a rush on the Gray's family's part to do anything in this case.

We have the luxury of being able to wait until all of the facts develop before we do anything, and that's what we've chosen to do so far.

BLITZER: One final question before I let you go. A change of venue. You can assume the lawyers for the six police officers, they'll seek a change of venue, arguing they can't get a fair trial in the city of Baltimore. How difficult will that be for those lawyers? And I ask you as an experienced attorney in Baltimore.

MURPHY: Well, motions like that are usually based on publicity. And it would be hard to find any place in Maryland that has not been saturated with the publicity that Baltimoreans have been saturated with.

After all, 99 percent of the publicity in this case comes from media, and media is ubiquitous. The same television stations that broadcast into Baltimore generally broadcast throughout the state. Same network television broadcasts throughout the state. And so what we're suspicious about is that this will be moved to avoid a mixed jury, and into, hopefully, an area on their part -- that's their hope -- where it's going to be a predominantly white jury, and that would be manifestly unfair and would aggravate tensions unbelievably. So people have to be very careful to apply the correct legal standard.

Now, the way it's normally done, by careful judges, is that they wait and see whether a fair and impartial jury can be impaneled in this jurisdiction and only if it can't be, should the case be removed. That is the proper legal standard, and of course, a fair and impartial jury can be impaneled in this jurisdiction.

BLITZER: Remember the Rodney King case. They moved that case out of Los Angeles to Simi Valley, because they didn't think they could get a fair and impartial jury in Los Angeles. So I don't know if that's going to happen this time, but I assume -- and I think you'll agree with me -- the attorneys representing the police officers will at least make that effort, right?

MURPHY: Oh, of course. They would be probably committing professional malpractice if they didn't at least try, but what I'm concerned about is what the proper legal standard would be for removal; and I think that was the sense of your question.

BLITZER: I think you're right. All right. Billy Murphy, thanks very much for joining us.

MURPHY: Thank you again, Wolf.

BLITZER: And please, pass along our best wishes to the family. As you point out, they're going through a great, great, great deal of pain, as all of us can appreciate. Thank you.

MURPHY: And, Wolf, thank you for those good wishes, and thank you for the restraint that you've shown as an analyst in this case.

BLITZER: Well, just trying to do our job. Appreciate it very much. We'll have you back. Billy Murphy is the attorney for the Freddie Gray family.

[17:25:04] Coming up, tonight's other breaking story. We're learning more about the suspects in a terror attack near Dallas, Texas. At least one, one of them linked himself to ISIS.

(COMMERCIAL BREAK)

BLITZER: Terror in Texas. They wore body armor. They carried assault rifles, and one declared loyalty to ISIS. Tonight, we're learning much more about the two gunmen who stormed a controversial event featuring depictions of the Muslim Prophet Mohammed. Both assailants were shot dead after wounding a security guard. And now it turns out that one of the gunmen was convicted in the past on a terror related charge, had social media links to ISIS and tweeted about the shooting before it even happened.

[17:30:10] Federal agents have been scouring the Phoenix apartment that they had shared before they set out on their trip to Garland, Texas, which is right outside of Dallas.

We have full coverage, and I'll speak live with Congressman Peter King of the Homeland Security Committee, but let's begin with the very latest. Our justice correspondent, Pamela Brown, is in Garland for us. What is the latest, Pamela?

PAMELA BROWN, CNN JUSTICE CORRESPONDENT: Well, Wolf, we have learned from sources that one of the two gunmen, Elton Simpson, had been on the FBI's radar for years, and in fact, an investigation had been reopened into him recently.

He was very active online, according to sources, corresponding with known ISIS finders. And in fact, just a couple hours before he drove here, with his accomplice and roommate, Nadir Soofi, he had tweeted about his links to a British ISIS jihadist with the hashtag #TexasAttack.

But beside that ominous tweet, Wolf, we have learned from sources that there was no indication the two men had been planning to come here to Dallas, this controversial exhibit showing cartoons of the Prophet Mohammed.

We have learned from officials that the two men pulled up here in the black sedan behind me here. There was a security guard and an officer stationed right at the entrance. When the men pulled up, the two officers got out of their car, and then the two suspects got out wearing bullet-proof vests, started opening fire from their assault rifles. We've learned the officer returned fire and shot and killed both of the suspects.

This investigation is ongoing. But Wolf, I can tell you that there was concern among law enforcement that this event was happening and that there was a joint bulletin sent out from the FBI and DHS in the days leading up to the event, talking about possible threats, even though they didn't know anything specific. There was great concern. And today the police here are credited the fact that they have a strong plan in place with being able to foil this attack. There were 200 people inside that event, Wolf. It could have been a lot worse.

BLITZER: Certainly could have been. All right. Thanks very much. We'll get back to you, Pamela.

FBI agents have been searching the Phoenix apartment where the two gunmen lived. Let's go live to our national correspondent, Kyung Lah. She's at that apartment building in Phoenix. What are you learning, Kyung?

KYUNG LAH, CNN CORRESPONDENT: Well, the FBI has been here throughout the day. You can see what they did overnight. This is the door leading to the apartment that the two men shared. You can see that the entire lock, the entire door, in fact, was blown open. Investigators were here throughout the day. They are, in fact, still talking to neighbors, still trying to piece together exactly how this entire plan was hatched.

As far as the people we've spoken to here, not too many people suspected these men. They said they were two young-ish sort of guys living in this community. They didn't have any outward signs of any sort of extremism.

One of the men, Elton Simpson, did very -- clearly posted he wanted to sell that dark sedan that was eventually used to drive to Texas. We also spoke to the mosque president, who said even though he knew about Elton Simpson's arrest in 2011, he thought that that may have been just a bad arrest, that he may have screwed up with the FBI. He did not see this coming. Here's what he told us.

(BEGIN VIDEO CLIP)

USAMA SHAMI, ISLAMIC COMMUNITY CENTER OF PHOENIX: You know, two members that they didn't show any signs of radicalization or any signs of even thinking about those things in that manner. So when that happens, you just it shocks you. You know? How good did you know these people? That's the question that people ask themselves.

(END VIDEO CLIP)

LAH: He knew Simpson for some ten years. He didn't know Nadir Soofi that long. He said he owned a local pizza shop, would show up at the mosque with his young son. But again, didn't have any sort of outward display, Wolf.

We also did talk to the attorney who represented Elton Simpson in that 2011 arrest, and she said, of all the people she's represented, she didn't think that he was the one who was going to take the step to violence -- Wolf.

BLITZER: We know that Elton Simpson, 30 years old, a convert to Islam; went by the name of Ibrahim. The second suspect, Nadir Soofi, 34 years old. What do we know about Nadir Soofi?

LAH: What we know about him is basically what the mosque told us. It is that he didn't appear to be married, because he never showed up at the mosque with his wife. He did show up with a young son. He had ties to the community, even though he didn't talk to a lot of people at the mosque. He had a pizza shop that people would eat at and buy pizza at. He seemed like a well-adjusted man. Even though he wasn't deeply involved in the mosque, they didn't hear any sort of radicalization from him.

BLITZER: Kyung Lah, thanks very much. We'll get back to you, as well.

Let's get some more now from Republican Congressman Peter King of New York. He's a member of both the Homeland Security and Intelligence Committees. [17:35:05] Congressman, thanks very much for joining us. I assume

you're getting briefed on what's going on from your intelligence law enforcement sources. What can you tell us about this terror attack outside of Dallas?

KING: Well, Wolf, basically what we're talking about here is, an attack that seems to have been certainly planned by these two in the past. The fact that they possessed the AK-47s, they knew exactly when to strike.

And that -- and also there seems to be contemporaneous social media contact. Almost after the attack. I've spoken to people who think it would be difficult for is, for instance to have been made aware that quickly of this attack, but this is still the early stages of the investigation.

But the fact that Simpson was apparently -- had involvement with al Shabaab going back several years ago. He now has an affinity for ISIS. The fact that there was this social media dialogue going on with ISIS members and other Islamists soon after the attack, all of this has to be fully, fully investigated. Clearly, I think this, at the very least, was ISIS-inspired.

BLITZER: It could have been so much worse, as you know, Congressman. Both of these gunmen, Nadir Soofi and Elton Simpson, they were, as you point out, wearing body armor. They were carrying assault rifles. You can only imagine what would have happened if they would have gotten into that building.

And Simpson himself was on probation after that 2011 conviction for making a false statement involving terrorism. The two had traveled over several state lines from Arizona to get into Texas, at Garland, Texas, outside of Dallas. I guess the question is, why weren't these two guys being watched more closely?

KING: Well, I'm one of those who thinks they should be. And again, I'm not aware of the particulars of this case, other than what's been made known up to now. But I do believe in having more surveillance of people in the Muslim community, because that's where the threat comes from.

But it's difficult to do, and certainly, if it's done too the courts can claim that this is unconstitutional interference. So I think the FBI probably goes about as far as they can in the world we live in today.

I think that they should be authorized to go further than that, especially in a case like this, where you have someone who was -- who did plead guilty to lying to the FBI about his terrorist connections.

So whether or not he could have been convicted on more than that at the time, certainly he becomes to me a person who should be watched, who should be surveilled, and also to see who he comes in contact with.

I think we as a country have to come to a realization that this is a war we're in, and that you have to -- you have to respect people's constitutional rights. You should not have this absolutely strict, strict interpretation. Because to me, it's very reasonable any time or total we have right now, a person who pleads guilty to a terrorism charge should receive more surveillance than the average person.

BLITZER: Congressman, I'm going to have you stand by. We have more to discuss about the alleged ISIS role in all of this. Much more with Congressman Peter King when we come back.

(COMMERCIAL BREAK)

[17:42:45] BLITZER: We're following the breaking news. Authorities have now identified both suspects in the terror attack near Dallas. Both lived in Phoenix. At least one of them linked himself directly to ISIS.

We're back with a key member of the House Homeland Security and Intelligence Committees, Republican Congressman Peter King of New York.

Congressman, one of these two gunmen, Elton Simpson, was on probation, as you know. He actually tweeted before the attack. He used the hashtag #Texasattack. He also posted a tweet, pledging loyalty to a British ISIS finder (ph). He was seemingly flaunting his terrorist intentions.

It's hard to believe. And at one point, he actually tweeted -- and I'll put this up on the screen, "May Allah accept us as Mujahideen." What do you make of that?

KING: It shows that he definitely was connecting himself to ISIS. Now whether or not ISIS knew about it in advance, that's going to be the question.

As I say, I think that -- that you may well find some direct links here, because of the fact that so soon after the attack, you find contemporaneous, almost contemporaneous social media contacts and discussion of this attack.

And, again, you know, we're at the early stages of this investigation, and I assure you the FBI is going through his apartments, and going through all his phone records, all his credit card bills, everything, to find out who he's been in contact with, where he's been. And this could again spread itself out exponentially. And that's what the FBI is looking at right now.

BLITZER: As you know, the head of the National Security Agency, the NSA, Admiral Michael Rogers, told CNN not long ago there are, in his words, blind spots in the U.S. ability to track terrorists inside this country. Would you say this is an example of that?

KING: This could be. I'm not certain if this is what Admiral Rogers was talking about. There are blind spots that I'm aware of. I don't know if this is one or not. I also know FBI Director Comey said there are FBI investigations of ISIS going on in all 50 states. Also, you have to remember that they were in Arizona. A number of the

9/11 hijackers spent a considerable period of time in Arizona also. So we have to look at that to see whether or not there's any other connections coming out of Arizona.

And again, this is all circumstantial, and some of it may end up nowhere. But these are the leads the FBI is going to follow. And I can assure you that.

[17:45:00] When I say the FBI, that means working with all the elements of our intelligence agency, including the NSA, CIA, everyone, to see what overseas connections there are and to see also if it goes just to ISIS itself or to affiliates in Europe.

BLITZER: How worried are you about copycats?

KING: Oh, we have to be. You have to be concerned about the trained person, the person who is actually working for ISIS, and those who just want to cause the type of incident like last night. I mean, as you mentioned before, this came so close to being a mass catastrophe, and you get some wannabe who sees the opportunity to make something in his eyes out of his life by killing a large number of people and seeing how easy it would be, yes, we have to be very concerned about that. That's, again, why it's so important we have as much constant surveillance as we possibly can.

BLITZER Peter King, the Congressman from New York, thanks very much.

KING: Wolf, thank you, as always. Thank you.

BLITZER Coming up, a CNN exclusive. We'll take you to what's been called the most dangerous place on earth, the Demilitarized Zone between North and South Korea, as the nuclear North warns that in any future war, America will become ground zero. We're going live to Pyongyang, North Korea.

(COMMERCIAL BREAK)

[17:50:41] BLITZER Now a CNN exclusive. A visit to what may be the most dangerous place on earth: the Demilitarized Zone between North and South Korea. But the nuclear North is warning that in any future war, America will become "ground zero."

CNN's Will Ripley toured the North Korean side of the border. He's joining us now live from the capital of Pyongyang.

Will, this is a major development. Tell us what you saw and what you learned.

WILL RIPLEY, CNN CORRESPONDENT: Wolf, as you know when you came here to North Korea, there's a lot of restrictions on travel. So when we learned yesterday that we would be taken to the Demilitarized Zone, the DMZ, the border between North and South Korea, and not only that, but we would be given remarkable access and the ability to speak with a military official who gave a very serious warning for the United States. Like troops heading into battle North Koreans follow banners heading into warning for the United States.

(BEGIN VIDEOTAPE)

RIPLEY (voice-over): Like troops heading into battle, North Koreans follow banners, marching into work. Mobilization is a part of daily life in this militarized nation.

(on camera): Right now we're on the main road heading south from Pyongyang towards the border between North and South Korea, an area known as the DMZ, the Demilitarized Zone.

(voice-over): The DMZ is anything but demilitarized. This barren road takes us to the cease-fire line that ended the brutal fighting of the Korean War in 1953. Today, a heavily fortified border with both sides constantly prepared for war.

LT. COL. NAM DONG HO, NORTH KOREAN ARMY: We're right here.

RIPLEY (voice-over): Junior Lieutenant Colonel Nam Dong Ho is part of North Korea's standing army of more than 1 million, nearly three quarters stationed close to the DMZ. Nam calls it the most tense place on the planet. More than 60 years after the cease-fire, North and South Korea are still technically at war.

HO: This is where you used to negotiate with the Americans.

RIPLEY (voice-over): Most Western historians said North Korea started the war. But here they teach a different version of history.

HO: (SPEAKING KOREAN)

RIPLEY (voice-over): (Translating) America is the real culprit, he says. But still, the Americans deny the truth.

The tension is palpable as we approach the border.

(on camera): Is there a real danger here of something breaking out?

HO: Yes.

RIPLEY (voice-over): Armed soldiers stand just feet from the border. The scene of occasional deadly violence in the years since the cease- fire. As we enter a building straddling the line between North and South, an ominous warning of an even bigger danger.

HO: (SPEAKING KOREAN)

RIPLEY (voice-over): (Translating)The Americans have been threatening us with nuclear weapons, he says, since the days of the Korean War.

(on camera): So is that why North Korea continues to develop its own nuclear program?

HO: (SPEAKING KOREAN)

RIPLEY (voice-over): (Translating) That's why we've equipped ourselves with nuclear weapons, he says, to counter the American nuclear threat. Nam points out no country with a nuclear weapon has ever been attacked.

A report leaked by "The Wall Street Journal" claims Chinese nuclear experts recently warned the U.S. They say Pyongyang now has 20 nuclear devices and is expected to double that number soon. North Korea also believed to possess long range missile technology.

HO: (SPEAKING KOREAN)

RIPLEY (voice-over): (Translating) If another major conflict breaks out between North Korea and the U.S., he says, America itself will become ground zero.

A six decade old war, considered history by much of the world, still a very real part of life on the DMZ. A painful reminder of the region's violent past, tense present and uncertain future.

(END VIDEOTAPE)

RIPLEY: On the ground here in North Korea, Wolf, I have to say that as we speak, not only to the military but to North Korean citizens as well, there's a tremendous amount of anger and resentment towards the United States here and a real feeling that the U.S. is to blame for much of this country's isolation and hardship due to economic sanctions, Wolf.

BLITZER And in Pyongyang, the capital, where you are now, what's it like? What's the mood over there?

RIPLEY: The mood here is one of optimism. People here in Pyongyang, while they, of course, would like to be more involved with the rest of the world, they feel that their standard of living has improved. They've had a good crop the past few years. People appear to be well fed.

You're seeing more cell phones in people's hands, you're seeing newer vehicles on the streets, people are wearing newer clothing and shoes. So it does appear that North Korea is trying to make progress economically, but yet you still hear that powerful military rhetoric that has continued to distance this country from other Western countries including the U.S.

[17:55:10] BLITZER We'll check back with you tomorrow. Good exclusive reporting. Not often that we get a live shot coming in from Pyongyang, North Korea. Will Ripley on the scene for us. Thanks very, very much.

And by the way, to our viewers out there, you can learn a lot more about Will's trip to North Korea. He's sharing exclusive photos and stories at CNN.com.

Coming up, confusion in the streets of Baltimore as a suspect is arrested and a gun goes off. Police rush to explain what happened, but just a day after a curfew is lifted, can they keep a lid on tensions? And Texas terror attack. New details about the gunmen who were killed as they attacked an event focused on the Muslim Prophet Muhammad. How much influence did ISIS have over this attack?